2D Metal-Free BSi 5 with an Intrinsic Metallicity and Remarkable HER Activity.

One of the most urgent and attractive topics in electrocatalytic water splitting is the exploration of high-performance and low-cost catalysts. Herein, we have proposed three fresh two-dimensional nanostructures (BSi ₅ , BSi ₄ , and BSi ₃ ) with inherent metallicity contributed by delocalized π electrons based on first-principles calculations. Their planar atoms arrangement, akin to graphene, is in favor of the availability of active atoms and H adsorption/deadsorption. Among them, the BSi ₅ monolayer shows the best HER activity, even superior to a commercial Pt catalyst. Moreover, its extraordinary HER activity can be maintained under high H coverage and large biaxial strain, mainly originating from the fact that B 2p _z orbital electrons are responsible for the B-H interaction. Further analysis reveals that there appears to be a linear correlation between the magnitude of B 2p _z DOS at the Fermi level and Gibbs free energy in both three proposed nanostructures and five hypothetical B-Si nanostructures. Our work represents a significant step forward toward the design of metal-free HER catalysts.